Date: Sat, 20 Oct 2007 16:47:20 -0700 From: "Len Gross" <sandiegobiker@gmail.com> To: "Julian Elischer" <julian@elischer.org> Cc: freebsd-net@freebsd.org Subject: Re: Disable Exponential Backoff (retry) on Ethernet? Message-ID: <27cb3ada0710201647y5104bd1fge2540c5fc1e2b49c@mail.gmail.com> In-Reply-To: <471A6B72.2030305@elischer.org> References: <27cb3ada0710172051t536a4d11pfdfdb079ebd98932@mail.gmail.com> <20071019224155.GI20308@server.vk2pj.dyndns.org> <20071020183000.E8153@knop-beagle.kn.op.dlr.de> <27cb3ada0710201108l5e717fdbhc9fab610cb2a047c@mail.gmail.com> <471A6B72.2030305@elischer.org>
next in thread | previous in thread | raw e-mail | index | archive | help
May have found what I need. lancereg.h references an AMD Ethernet chip that appears to have a register you can set to enable/disable retry. So, I would just have to find some NICs that use this chip. A task for later in the project. Thanks to all for the discussion. -- Len On 10/20/07, Julian Elischer <julian@elischer.org> wrote: > > Len Gross wrote: > > If I have to, I will employ some form of simulation of collisions, but > that > > will have to be done carefully in order to get the effect of collsions > > beteen multiple stations without messing up timing. > > > > I REALLY wanted to have the PHY handle it. Usng half duplex and some > old > > hubs (if I can find one) would get collisions, but the retry would > create > > other problems. > > > > So, looks like "simulated" collisions will be the way to go. > > > > BTW: I'm using Netgraph - very cool stuff. > > > > --Len > > > > thankyou :-) > > > > > > > > > On 10/20/07, Harti Brandt <hartmut.brandt@dlr.de> wrote: > >> On Sat, 20 Oct 2007, Peter Jeremy wrote: > >> > >> PJ>On Wed, Oct 17, 2007 at 08:51:34PM -0700, Len Gross wrote: > >> PJ>>I'm doing some protocol development and it is convenient to start > it > >> on > >> PJ>>Ethernet. I will need to send a packet to the Ethernet device and > >> only have > >> PJ>>it be sent once, even if there is a colision. > >> PJ> > >> PJ>I know we've still got some hubs lying around in a backroom at work > >> PJ>but I don't know of anything that will let you disable the > retry-on-CD. > >> PJ> > >> PJ>Have you considered simulating the network at a slightly higher > lever: > >> PJ>Use ipfw pipes or similar to simulate packet loss (either set a > queue > >> PJ>length of 1 or probabilistically). This could be done either as a > >> PJ>bridge or by tunneling your protocol over IP or UDP. > >> > >> Some years ago I wrote a netgraph node that connected to ethernet nodes > >> and simulated a wireless broadcast channel including collisions, > >> timevariable delay, loss and shaping. Can be done in a couple of > hundreds > >> of lines and easily allows >100MBit/sec with gigabit ethernet. The > >> ethernet is just the physical transport medium for the packets and does > >> not take part in the emulation. All that was controlled by bsnmpd and a > >> remote command line tool and/or Java-GUI. Unfortunately I cannot > release > >> this (yet) due to licensing... > >> > >> harti > >> > > _______________________________________________ > > freebsd-net@freebsd.org mailing list > > http://lists.freebsd.org/mailman/listinfo/freebsd-net > > To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org" > >
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?27cb3ada0710201647y5104bd1fge2540c5fc1e2b49c>